The London Encyclopædia: Part II. The Practise of Dyeing. Of Dyeing Crimson.

The London Encyclopædia: Part II. The Practise of Dyeing. Of Dyeing Crimson.

Kappale teoksesta:

The London Encyclopædia, or Universal Dictionary of Science, Art, Literature, And Practical Mechanics, Comprising A Popular View of The Present State of Knowledge.

By The Original Editor of The Encyclopædia Metropolitana, Assisted By Eminent Professional And Other Gentlemen.

In Twenty-Two Volumes

Vol. VII

Printed For Thomas Tegg, 73, Cheapside;
R. Griffin & Co., Glasgow; Tegg and Co., Dublin; Also J. & S. A. Tegg, Sydney and Hobart Town.


Part II. The Practise of Dyeing. Of Dyeing Crimson.
s. 611-612

198. The different processes employed for obtaining the various shades of crimson, from the deepest to the ligtest, may be reduced to two. Either the shade of crimson required is given to cloth previously dyed scarlet, or the cloth is at once dyed crimson. Alum, salts with earthy bases, and fixed and volatile alkalis, have the property of changing the color of scarlet to crimson, which is the natural color of cochineal. Nothing more, therefore, is necessary, than to boil cloth dyed scarlet for about an hour in a solution of alum, proportioned in strenght to the deepness of the color desired. But as other salts with earthy bases have the same property, and water contains more or less of these salts, whence it gives a proportionate rosy tinge to scarlet passed through it, particularly if it be worn, the quantity of alum necessary to obtain a crimson varies according to the nature of the water employed: and, when well charged with these salts, it will answer the purpose of itself, without the addition of alum. If a piece of scarlet have any defects, it is most convenient to convert it into a crimson.

199. Hellot says, that he has tried soap, soda, potassa, and crude potassa; that all these substances produced the crimson desired, but saddened it, and gave it less lustre than alum. Ammonia, on the contrary, produced a very good effect; but, as it evaporates quickly, a considerable quantity must be put into the bath a little more than warm, a little ammoniacal muriate, or sal ammoniac, and common potash. By this method the cloth instantly took a very bright rosy color. He thinks that it heightens the color so much as to render less cochineal necessary. But M. Poerner, who gives the same process, directs the scarlet to be left twenty-four hours in a cold solution of potassa and ammoniacal muriate.

200. To dye crimson at once, a solution of two ounces and a half of alum, and one ounce and a half of tartar, to every pound of cloth, is used for the boiling: and the cloth is afterwards dyed with an ounce of cochineal. Solution of tin is commonly added, but in less proportion than for scarlet. The processes employed vary greatly, according as the shade required is deeper or lighterm or more or less distant from scarlet. Common salt is also used for the boiling by some dyers. For saddening crimsons, and giving them more bloom, archil and potassa are frequently used, but the bloom thus imparted is not permanent. Sometimes the boiling for crimson is made after a scarlet reddening, by adding tartar and alum: and it is said, that the win soup color has more bloom, if both its boiling and reddering he made after scarlet, than when it is dyed in a fresh bath. For these colors the wild cochineal may be used instead of the fine, but in greater quantity. The reddening which has been used for crimson may also be employed for purples, and other compound colors.

Both scarlets and crimsons in half-gram, are made by substituting madder for half the quantity of the cochineal, giving the same boiling as for scarlet in grain, and folloring in other respects the processes for reddening the scarlet or crimson. Other proportions of madder may be used instead of half, according to the effect desired. The common madder red also acquires a greater lustre, when its boiling is made after reddening for scarlet.

201. In silk the grain crimson, produced by cochineal, is distinguished from dalse crimson, which is obtained by Brasil-wood. Silks that are intended to be dyed crimson with cochineal, should not be boiled with more than twenty pounds of soad to 100 pounds of silk, as the slight yellow vast which silk has, when only so far scoured, is advantageous to the color. After the silk has been well cleansed from the soap, it is to be put into an alum liquor of the full strenght. In this it is commonly left from the evening till the next morning; it is then washed, and twice beetled at the river. In preparing the bath, an oblong boiler is filled with waterm to about one-half of two-thirds; and, when the water boils, white galls powdered are thrown in, from half an ouce to two ounces for every pound of silk. After boiling a few moments, from two to three ounces of cochineal, powdered and sifted, for every pound of silk, according to the shade required, are put in, adding afterwards an ounce of tartar, to every pound oc cochineal; and when the tartar is dissolved, an equal quantity of the solution of tin. This solution ought to contain more tin than that used for scarlet, otherwise the colors will be too bright. Macquer directs this solution oto be made with sixteen parts of nitric acid, two of ammoniacal muriate, as much fine grain tin, and twelve of water. These ingredients are mixed and boiler is filled up with cold water. In this the silk is immediately dipped, and turned on the skein stircks till it appears to be of a uniform color. The fire is then increased, and the bath made to boil for two hours, turning the silk from time to time. After this the fire is put out, and the silk put into the bath, where it is kept a few hours longer. The silk is afterwards washed at the river, twice beetled, wrung and dried. When crimsons are to be browned, they must be passed, after having been washed, through a slution of sulphate of iron, more or less strong according to the shade required. If it should have a yellow tinge, the solution must be charged with a greater or less proportion of decoction of fustet or Venus's sumach. White galls should be chosen, because black ones would dull the color of the crimson; and even too large a quantity of the white will produce the effect. Macquer says, that the galls serve only to increase the weight of the silk: yet their general effect is to reader colors


more permanent, and they are essentially becessary for crimsons that are intended to be browned. Vinegar is employed as a test in distinguishing grain crimsons from dalse: but it will not detect colors obtained from Brasil-wood, if they be fixed by means of solution of tin; for in this case they resist vinegar as well as those made with cochineal. A very small quantity of solution of tin is, therefore, put into the bath for dyeing silk crimson. If the same process as that for dyeing wool scarlet were employed, the silk would lose its bloom, and acquire only a faint color. Macquer and Scheffer have, however, detailed processes which differ from it only in a few circumstances, for dyeing silk rose and poppy colors by solution of tin, used cold, that its action on the silk might not be too powerful.

202. Brazil-wood is used for dyeing silk what is called false crimson, to distinguish it from that produced by cochineal, which is much more permanent. For this process the silk should be boiled with soap, in the proportion of twenty pounds of the latter to 100 pounds of the former, and afterwards alumed. Less aluming is required for this than for grain crimson. Having washed it in running water, it is dipped in a bath, more or less charged with Brasil juice, according to the shade to be given. In the preparation of the bath hard water is preferable to soft, as it produces with the dye-stuffs a fuller crimson. Washing the silk in hard water will produce nearly the same effect. In order to make false crimson deeper, or dark red, a decoction of logwood is added to the Brasil bath, after the silk has been impregnated with the latter. A little alkali may also be put in according to the shade required. But to imitate poppy or fire color, the silk must have an anotta ground, even deeper than when it is to be dyed with carthamus: after which it is washed, alumed, and dyed with the decoction of Brasilwood, to which a small portion of soap is generally added. We might here enumerate several other processes for imparting the crimson color, but the above, with what we have said respecting the dyeing of reds in general, and of scarlet in particular, render it unnecessary to enlarge.

Ei kommentteja :